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### Author Topic: how can I find the amp hours?  (Read 1721 times)

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#### xboogerx

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##### how can I find the amp hours?
« on: May 23, 2008, 08:36:14 PM »
I have to 2 lawn and garden batteries. both are the same and brand new.

both 12v
cranking amps: 350
cold cranking amps: 275

How can I figure out the amp hours?

I've got two 10.5 amp wheelchair motors needing 24v, are these batteries going to be enough to run for like 2hrs straight??
thanks

#### Nyx

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##### Re: how can I find the amp hours?
« Reply #1 on: May 23, 2008, 08:40:47 PM »
I've got two 10.5 amp wheelchair motors needing 24v, are these batteries going to be enough to run for like 2hrs straight??

It's unlikely you'll be able to run your motors at full-power for 2 hours, but then what robot runs around at maximum speed for that length of time?

#### xboogerx

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##### Re: how can I find the amp hours?
« Reply #2 on: May 25, 2008, 02:27:47 PM »
so is there a way to find out my amp hours for these batteries?

#### Admin

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##### Re: how can I find the amp hours?
« Reply #3 on: May 30, 2008, 08:24:28 PM »
It should be written on the battery. Or look up the datasheet.

Otherwise, get a big power resistor (P=V*I) and short the battery. Use a multimeter to measure current.

amp hours = current * hours that the battery supplied that current

edit: I said something extra dumb, so I'm hiding it
« Last Edit: May 31, 2008, 04:48:53 PM by Admin »

#### Soeren

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##### Re: how can I find the amp hours?
« Reply #4 on: May 31, 2008, 03:54:38 PM »
I have to 2 lawn and garden batteries. both are the same and brand new.

both 12v
cranking amps: 350
cold cranking amps: 275

How can I figure out the amp hours?

I've got two 10.5 amp wheelchair motors needing 24v, are these batteries going to be enough to run for like 2hrs straight??
thanks
With a CCA rating of 275A, the capacity should be in the range of around 20Ah (give or take).
That's worth less than 1 hour, since the capacity only holds for a lower current drain. Most batteries re specified by the 20 hour rate, some by the 5 hour rate. Any higher drain results in less capacity, so you'll need more than double your present capacity, at least if you wanna drain 10.5A continuously for 2 hours without pause.

If the batteries doesn't have the specs stamped on them, try Googling for their name and model. You should be able to find the specs for most common lead-acid batteries.
Regards,
SÃ¸ren

A rather fast and fairly heavy robot with quite large wheels needs what? A lot of power?
Please remember...
Engineering is based on numbers - not adjectives

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